/Engine/Plugins/Online/OnlineFramework/Source/Party/Public/SocialToolkit.h
void NotifySubsystemIdEstablished ( [USocialUser](API\Plugins\Party\User\USocialUser) & SocialUser, [ESocialSubsystem](API\Plugins\Party\ESocialSubsystem) SubsystemType, const [FUniqueNetIdRepl](API\Runtime\Engine\GameFramework\FUniqueNetIdRepl) & SubsystemId )